1. Field of the Invention
The present invention is generally related to an apparatus for punching. More particularly, this invention is related to an apparatus for punching slots into profiled cellular polyvinylchloride (cellular PVC) boards, wherein an exemplary application of such punched, profiled cellular PVC is in the use as siding.
2. Background of the Invention
This invention relates to a novel apparatus for punching slots into profiled cellular PVC boards to be used as siding. Slot punching of cellular PVC boards at the required production throughput rate demands an entirely unique approach to achieve the required slot punching accuracy as compared to prior art punching apparatuses used to punch traditionally used rigid vinyl siding materials.
Conventional high speed rigid rotary vinyl siding slot punching consists of a single rotary punching wheel, combined with two lower stationary side cutting blades. This conventional arrangement is typically located just downstream of the extruder on a vinyl siding extrusion line, punching through just extruded, warm vinyl. The geometry of this conventional arrangement shears the slot sides but does not perform actual punch/die shearing of the slot ends. In warm, newly extruded vinyl, this lack of shearing of the slot ends does not pose a problem and slots are punched with relatively clean slot ends.
Profiled cellular PVC boards are milled from previously extruded cellular PVC sheets. The material has been cured and is therefore harder and more brittle than warm cellular PVC. Profiled cellular PVC boards punched with the above described conventional arrangement, show significant breakage along the shear line, uneven cuts and structural fractures in the slot vicinity due to not fully shearing the entire slot. Therefore, the conventional slot punching arrangement is totally inadequate for forming slots in cellular PVC boards. Accordingly, a new approach is needed that would punch slots in cellular PVC material at the required rates, wherein all of the exposed sides of the slot are sheared. Additionally, specially contoured and coated tooling is required when punching cellular PVC material due to its highly abrasive qualities, as compared to conventional vinyl siding material.